On-line color monitoring and control system and method

ABSTRACT

An on-line color monitoring and control system and method includes feeding of colorant in a given amount or ratio in order to achieve a desired color of a product. The system and method described here achieve reliable on-line color control of synthetic fibers, single moving yarn (or fiber) or a collection of moving fibers. The color characteristic of the product is sensed and processed to generate a control signal for adjusting the amount of colorant being fed. Color measurement takes place either prior to or after spooling of the product.

TECHNICAL FIELD

The present invention generally relates to on-line color monitoring andcontrol of fibers produced by an extrusion device. More specifically,the invention relates to the measurement of the color of moving yarn orfibers soon after extrusion. Two alternative sensor mechanisms aredisclosed--one which measures color prior to spooling of the product,and another which measures color after the product is collected on thespool. In addition, the color measurement signal is quickly checkedagainst a reference signal using an optical switch.

BACKGROUND ART

In the past, the color of a product produced by an extrusion device hasbeen monitored and controlled in an off-line manner. Typically, theextrusion device or system would be operated until color equilibrium wasachieved, followed by collection of a product having a certain color.The spool of collected product would then be removed from the system,and taken to a color laboratory where the color would be measured usingan off-line spectrometer. Then, once a color evaluation was made, thespool would be returned to the extrusion device or system, adjustmentswould be made to the level of the colorant provided to the extrusiondevice, and another run of about ten minutes or so would be commenced.This process would be repeated until evaluation of the color of theproduct in the color laboratory indicated that the desired color, withinacceptable limits, had been achieved.

The latter process was not only time-consuming and inefficient, but alsoresulted in substantial waste. That is to say, a large amount of scrapmaterial was produced and wasted during each run. Thus, if several runsduring a given period of time were necessary in order to evaluate andadjust the color of the product, a very substantial amount of wastematerial would result.

The latter system or process was also inefficient from the standpoint oftime in that each run would take about ten minutes or so, and then thecolor evaluation in the laboratory would take another thirty minutes toone hour. Thus, if several repetitions of the evaluation process werenecessary before the final acceptable coloration was achieved, theentire pre-production process could take several hours.

Accordingly, there has been a need for the development of an on-linecolor monitoring and control system and method. Moreover, there is aneed for the development of such an on-line color monitoring and controlsystem and method employing the most modern optical technology for bothtransmission of incident light toward the product and reflection oflight from the product, as well as handling and transfer of the lightthrough an optical spectrum analyzer to that portion of the system whichactually performs the evaluation of the coloration of the product.

It is recognized that on-line measurement of the color of extrudedpellets in compounding operations is known in the art. For example, seethe following: U.S. Pat. No. 3,972,854--Costolow and U.S. Pat. No.5,559,173--Campo. In addition, on-line color control of fiber extrusionhas been achieved by measuring the color of a fiber melt. In thisregard, see U.S. Pat. No. 4,684,488--Rudolph.

Nevertheless, measurement of the color of moving yarn or fiber (or afilament of a yarn), or of a collection of fibers, is not known in theprior art. Moreover, the employment of alternative sensor mechanisms formeasuring color of an extruded product prior to spooling and on-spool,respectively, is also not known in the art. Finally, employment of meansfor quickly checking the color measurement signal against a referencesignal, and specifically use of an optical switch to accomplish thatpurpose, are also not known in the art.

Therefore, there is a need in the art for development of an on-linecolor monitoring and control system and method which measures the colorof moving yarn or fiber (or filament of a yarn), or of a collection offibers. Mechanisms for measurement of color both prior to spooling andon-spool are also needed. Finally, a means for quickly checking thecolor measurement signal against a reference signal, using an opticalswitch, is also needed.

The following patents are considered to be of background interestrelative to the present invention, and are burdened by the disadvantagesof prior art methods and arrangements, as discussed above: U.S. Pat. No.5,526,285--Campo et al.; U.S. Pat. No. 5,468,586--Proper et al.; U.S.Pat. No. 5,387,381--Saloom; U.S. Pat. No. 5,282,141--Faas et al.; U.S.Pat. No. 5,092,168--Baker; U.S. Pat. No. 5,053,176--Cameron et al.; U.S.Pat. No. 4,788,650--Willis et al.; U.S. Pat. No. 4,761,129--Aste et al.;U.S. Pat. No. 4,745,555--Connelly et al.; U.S. Pat. No.4,688,178--Connelly et al.; U.S. Pat. No. 3,388,261--Roberts et al.;

DISCLOSURE OF INVENTION

The present invention generally relates to an on-line color monitoringand control system and method, and more particularly to a system andmethod for measuring the color of a product produced by an extrusiondevice, determining whether the color falls within acceptable limits,and increasing or decreasing the level of the colorant provided to theextrusion device so as to adjust the color of the product.

As discussed in more detail below, the system of the present inventionis utilized with an extrusion system. More importantly, the system ofthe present invention employs a color sensing arrangement which, inconjunction with an optical spectrum analyzer (OSA), provides a colorsensor signal to a module (typically, a digital computer). The latterprovides a serial data output to a programmable logic controller (PLC),which provides control signals to the feeder/mixer arrangement of theextrusion system for the purpose of adjusting the colorant level of theraw material provided to the extrusion device. Finally, in accordancewith the invention, the PLC also provides an output to a network for thepurpose of providing status information and the like.

It is to be further understood that, in accordance with the invention, aspecially designed optical switch is provided for selecting between areference signal and a measurement signal so as to provide acorresponding output to the OSA or spectrometer. In addition, in oneembodiment, the inventive system employs a spring-loaded, twin-rollermeasuring arrangement for a light receiver so as to perform colormeasurement "on spool," and to provide a light measurement signal to theOSA. In a further embodiment of the invention, a yarn guide is employedand color measurement is performed prior to spooling of the material inquestion. Finally, in accordance with the invention, the colormonitoring and control system is software-controlled via a programmedelement or PLC connected, via a serial data communications link, to apersonal computer.

Therefore, it is a primary object of the present invention to provide anon-line color monitoring and control system and method.

It is an additional object of the present invention to provide a systemand method for measuring the color of a product produced by an extrusiondevice.

It is an additional object of the present invention to provide a systemand method which determine whether the color of an extruded productfalls within acceptable limits.

It is an additional object of the present invention to provide a systemand method which increases and decreases the level of colorant providedto an extrusion device so as to adjust the color of the extrudedproduct.

It is an additional object of the present invention to provide a colormonitoring and control system which employs a specially designed opticalswitch for selecting between a reference signal and a measurementsignal.

It is an additional object of the present invention to provide a colormonitoring and control system which, in one embodiment employs aspring-loaded, twin-roller measuring arrangement to provide "on spool"color measurement of a product.

It is an additional object of the present invention to provide a colormonitoring and control system which, in another embodiment, employs ayarn guide to perform color measurement prior to spooling of the productin question.

It is an additional object of the present invention to provide a colormonitoring and control system which is software-controlled via use of aprogrammed element, such as a PLC, connected via a data communicationslink to a personal computer.

The above and other objects, and the nature of the invention, will bemore clearly understood by reference to the following detaileddescription, the associated drawings, and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general block diagram of the color monitoring and controlsystem of the present invention.

FIG. 2 is a diagrammatic representation of the on-line color sensoremployed in the system of FIG. 1.

FIG. 3 is a diagram of an optical switch employed in the on-line colorsensor of FIG. 2.

FIG. 4 is a side, cross-sectional view of a bobbin and roller, showinguse of the twin-roller measuring arrangement of the present invention.

FIG. 5A is a perspective view of a yarn guide employed in the colorsensor of the present invention.

FIG. 5B is a further view of the yarn guide of the present inventionemployed with a fiber bundle for the purpose of transmission of light tothe yarn guide and reception of sensed light from the yarn guide.

FIGS. 6A and 6B are flowcharts of software operations performed by themodule (personal computer) and PLC in accordance with the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will now be described in more detail with reference to thevarious figures of the drawings.

FIG. 1 is a general block diagram of the color monitoring and controlsystem of the present invention. As seen therein, the on-line colormonitoring and control system 10 comprises feeders 12 and 14 connectedvia control valves 16 and 18, respectively, to a mixer 20. The mixer 20has its output side connected to an extruder 22, and the extruded outputmaterial thereof proceeds past a line break sensor 24 to a spool 26, onwhich the extruded material is wound.

The system 10 further includes a color sensor 28 disposed adjacent tothe spool 26, the output of the color sensor 28 being connected via anoptical spectrum analyzer (OSA) or spectrometer 30 to a module 34, whichis implemented by a computer. The output of module 34 is connected tothe input of programmable logic controller (PLC) 36, and the output ofPLC 36 is provided to a network 38. In addition, the PLC 36 providescontrol outputs to the control valves 16 and 18, respectively.

In operation, feeder 12 is typically loaded with raw material, such asnylon material, to be mixed and extruded, while feeder 14 is typicallyloaded with colorant in order to provide coloration of the material fromfeeder 12 once the two constituents are mixed in mixer 20. In responseto control signals from PLC 36, valves 16 and 18 provide a correspondingflow of nylon raw material and colorant from feeders 12 and 14,respectively, to the mixer 20, in which those materials are mixed. Theresultant mixed material is then provided to an extruder 22 which, inaccordance with a conventional extruding process, produces extrudedmaterial which is conveyed past the line break sensor 24 to the spool26, on which the extruded material is wound.

Color sensor 28, which is disposed adjacent to the spool 26, operates ina manner to be described in more detail below to generate an opticalsignal output corresponding to the color of the material wound on spool26 as sensed by the sensor 28. The optical signal output of sensor 28 isprovided to OSA 30, wherein it is converted into an analog electricalsignal output for provision to the module 34.

As previously mentioned, module 34 is, preferably, a computer whichreceives the analog signal input from OSA 30, converts it into digitalform, and then provides a corresponding serial data output to the PLC36.

PLC 36 operates, in a manner to be described in more detail below, todetermine the coloration of the material wound on spool 26, compare itto a desired coloration within acceptable standards, and generatecontrol signals for adjusting the flow rate of the nylon material infeeder 12 and/or the colorant contained in feeder 14 (via valves 16 and18, respectively) in order to vary the input to mixer 20, and thus varythe coloration characteristics of the mixed material provided by mixer20 to extruder 22. In addition, PLC 36 provides an information output toa network 38 for dissemination to various personnel involved in orresponsible for the operation of the on-line color monitoring andcontrol system 10.

Keyboard 32 is provided in order to receive operator inputs to thesystem 10, and provides such operator inputs to the module 34. Suchoperator inputs are provided in order to initiate the operation of thesystem 10, to set parameters (such as initial feed settings for feeders12 and 14), and to control the operation of the system during theon-line color monitoring process.

Line break sensor 24 is a conventional device for sensing a break in theline of extruded material provided by extruder 22 to the spool 26. Ifthere is such a break, sensor 24 operates in a conventional manner toprovide an alert signal to the module 34.

FIG. 2 is a diagrammatic representation of the on-line color sensoremployed in the system of FIG. 1. As seen therein, on-line color sensor28 comprises a measurement spool arrangement 50 and a white referencearrangement 52 in combination with optical fiber connections 54, 56, 58and 60 and optical switch 62. As seen in FIG. 2, a light source 64provides an optical input to both measurement spool arrangement 50 andwhite reference arrangement 52. More specifically, the light output ofsource 64 is provided via optical fiber connections 58 and 60 tomeasurement spool arrangement 50.

The measurement spool arrangement 50 transmits the light toward thematerial being wound on spool 26 (FIG. 1), and receives reflected lighttherefrom. The reflected light is provided via optical fiber connections54 and 56 to one input of the switch 62, the other input of whichreceives white reference light reflected from white referencearrangement 52 as a result of the reception, by arrangement 52, ofincident light from the light source 64.

Optical switch 62 operates, in a manner to be described in more detailbelow, to select either the reference light from arrangement 52 or thereflected measurement light from measurement arrangement 50 for input tothe OSA 30.

FIG. 3 is a diagram of an optical switch employed in the on-line colorsensor of FIG. 2. As seen therein, optical switch 62 comprises thefollowing elements: lever 81, motor shaft 82, optical fiber connector83, grooved track 84, frame 85, contact element 86, microswitches 87aand 87b, optical fiber inputs 88 and 89, optical fiber output 90, andmotor 91.

In operation, motor 91 drives lever 81 alternately between positions 84aand 84b in the grooved track 84. That is to say, lever 81 is firstdriven in the direction of arrow A so as to come to rest in position84a, and is then driven in the direction of arrow B so as to come torest in position 84b. In position 84a, the optical fiber input 88 frommeasurement arrangement 50 (FIG. 2) is connected to the optical fiberoutput 90. Alternatively, in position 84b, the optical fiber input 89from reference arrangement 52 (FIG. 2) is connected to the optical fiberoutput 90. Optical fiber output 90 provides its optical fiber output tothe OSA 30, as previously described above with respect to FIGS. 1 and 2.

Further referring to FIG. 3, when the optical fiber connector 83 oflever 81 is in position 84a, contact element 86 contacts microswitch87a, thereby providing an information signal to module 34. Similarly,when optical fiber connector 83 of lever 81 is in position 84b, thecontact element 86 contacts microswitch 87b, thereby providing a furtherinformation signal to module 33.

Motor 91 is programmed or controlled to alternately rotate motor shaft82 in one of two directions, as indicated by the double-headed arrow Cin FIG. 3. In this manner, the lever 81 and its associated optical fiberconnector 83 are moved alternately in the directions indicated by thearrows A and B, respectively. That is to say, motor 91 moves lever 81 inthe direction indicated by arrow A in FIG. 3 until it reaches position84a, where it is stopped by the endwall of the slot 84. Similarly, motor91 moves lever 81 in the direction indicated by arrow B until it reachesposition 84b, where it is stopped by the endwall of slot 84.

With respect to the operation of the motor 91 of FIG. 3, preferably,motor 91 is normally driven in the clockwise direction by a drive signalfrom module 34 of FIG. 1. The motor 91 drives the lever 81 through arubber linkage 82a (seen in FIG. 3) so that, once the lever 81 has beenstopped by the endwall of slot 84 at position 84a, motor 91 continues todrive and puts the rubber linkage 82a in torsional tension, therebyfirmly pressing the lever 81 against the right hand endwall of slot 84at position 84a. When rod 86 arrives at its leftmost position andcontacts microswitch 87a, an information signal is sent to module 34(FIG. 1), and the module 34 cuts off the motor 91.

Preferably, motor 91 is a stepper motor, which has a holding torque whennot moving so that the rubber linkage 82a is held in light torsion andthe lever 83 is pressed against the end of the slot 84. In position 84a,a color measurement signal received via input optical fiber 88 isprovided via output optical fiber 90 to module 34. Holding the lever 83with positive pressure against the end of the slot 84 gives good opticalalignment repeatability, and this has been estimated to be better thanfifty micrometers.

With respect to the second cycle of operation of the lever 81 and motor91, the module 34 is programmed so that, after a predetermined period oftime (for example, once every hour or so), the motor 91 is driven bymodule 34 in the counter-clockwise direction, thereby changing theposition of the lever 83. In this manner, the lever 83 is driven in thedirection of arrow B so as to arrive at position 84b in grooved track84. At that point, rod 86 contacts microswitch 87b so that module 34cuts off motor 91, and module 34 takes a measurement of the referencesignal provided via input optical fiber 89 (FIG. 3) and output opticalfiber 90. Once the measurement of the reference signal is taken, module34 places optical switch 62 into its original state so that anothermeasurement cycle can commence.

FIG. 4 is a side, cross-sectional view of a bobbin and roller, showinguse of the twin-roller measuring arrangement of the present invention.As seen therein, the twin-roller measurement arrangement 50 comprisesrollers 100 and 101 which are joined by a connecting frame 102 which isurged in a direction toward the spool 26 by a spring 103. Lightgenerated by the source 64 (FIG. 2) is conveyed to a point locatedbetween the rollers 100 and 101 by optical fiber 50a, and lightreflected from the material wound on the spool 26 is conveyed away froma position between rollers 100 and 101 by optical fiber 50b and, aspreviously mentioned, is provided via optical fiber connectors 54 and 56and optical fiber input 88 to the optical switch 62 (FIG. 2).

In operation, spool 26 is rotated under the influence or urging of arotating support 104. Preferably, rotating support 104 is firmly fixedin space and cannot move except for rotation. The spool 26 is free tomove away from support 104 as it grows. The center of spool 26 actuallytraces an arc in the plane of FIG. 4 (if such an arc were to beplotted). Thus, in the preferred embodiment, pivoting action betweenconnecting frame 102 and spring 103 takes place via the pivotalconnection 103a therebetween.

It should be recognized that, although not shown in FIG. 4, the spool 26has a motor attached to its central axle 26a so that the spool 26 isrotatable. Moreover, the entire arrangement--spool 26, axle 26a and thespool motor (not shown)--is movable as the spool 26 rotates and isfilled, and thereby moves away from the rotating support 104 in thedirection generally indicated by the arrow D in FIG. 4.

The twin-roller arrangement 50 is maintained in its position withrespect to the rotating spool 26 as a result of the combined influenceof the spring 103 (which urges the rollers 100 and 101 toward the spool26) and the rotational capability of the rollers 100 and 101. As thespool 26 and the material wound thereon pass by the rollers 100 and 101,light provided by source 64 (FIG. 2) is conveyed via optical fiber 50aso that the light is incident on the surface of the material wound onspool 26. As a result, light is reflected from the material on spool 26,and such reflected light is conveyed away from spool 26 and rollers 100,101 by optical fiber 50b. Such reflected light, as previously mentioned,is conveyed via optical fiber connectors 54 and 56 and optical fiberinput 88 to the optical switch 62.

FIG. 5A is a perspective view of a yarn guide employed in the colorsensor of the present invention. The arrangement shown in FIG. 5Aconstitutes an alternative embodiment for light measurement, that is, analternative to the twin-roller measuring arrangement 50 generally shownin FIG. 2 and described in more detail relative to FIG. 4.

As seen in FIG. 5A, yarn guide 120 comprises a U-shaped light shield 122which, on one side thereof, receives a fiber optical bundle 124. Astainless steel block 126 having a slot 128 formed therein is mounted onan interior surface of the U-shaped light shield 122.

In operation, material emerging from the extruder 22 (FIG. 1)--forexample, yarn 130 shown in FIG. 5A--is conveyed through the slot 128, inwhich the yarn 130 passes adjacent to illuminating fibers 124a containedwithin the bundle 124. Illuminating fibers 124a convey light toward theyarn 130 so as to illuminate the yarn 130, and light reflected therefromis conveyed back through receiving fibers 124b in the bundle 124. Oncethe yarn 130 passes adjacent to fiber optic bundle 124, it is conveyedout the lower end of yarn guide 120 toward the spool 26.

FIG. 5B is a further view of the yarn guide of the present inventionemployed with a fiber bundle for the purpose of transmission of light tothe yarn guide and reception of sensed light from the yarn guide. Inaccordance with this embodiment of the invention, the yarn or fiber 130is subjected to color measurement just as the individual extrudedfilaments 132 emerging from the extruder 22 (FIG. 1) are collectedtogether. Filaments 132, once collected, form a neat reproducible ribbonof yarn 130, and are measured just before they pass through aconventional lubrication applicator (not shown).

The ribboned yarn 130 is measured, as previously described, by shiningwhite light from source 64 (FIG. 2) on the yarn 130, and measuring thereflected or scattered light by conveying such reflected or scatteredlight through optical switch 62 to the OSA 30 (FIG. 2). In practice, afiberoptic bundle 124 is utilized and, as previously described, thebundle 124 has half of its elements in the form of illuminating fibers124a and the other half of its elements in the form of receiving fibers124b (see FIGS. 5A and 5B).

FIGS. 6A and 6B are flowcharts of software operations performed by themodule (personal computer) and PLC in accordance with the presentinvention.

More particularly, FIG. 6A is a flowchart of the operations performed bythe module 34 of FIG. 1. In that regard, module 34 of FIG. 1 is,preferably, a programmed personal computer which receives analog colorsensor signals from the OSA 30. Accordingly, module 34 is equipped withan analog-to-digital converter (ADC) card or other means for digitalconversion, thereby converting the analog color sensor signals from theOSA 30 to digital form prior to provision to the processor of thepersonal computer or module 34. Such digital data are then processed bythe processor of the personal computer or module 34 in accordance withthe flowchart of FIG. 6A.

Considering the flowchart of FIG. 6A in detail, the processing operationis commenced (block 200), and a target color is selected from a list oftarget colors (block 201). This selection of a target color is typicallyperformed in response to an operator input via keyboard 32 of FIG. 1.

Continuing with the flowchart of FIG. 6A, in the manner described above,the color of the product wound on spool 26 is measured (block 202), andan error or disparity between the measured color and the target color iscalculated (block 203). A determination is then made as to whether ornot the measured color falls inside a tolerance band or acceptable limitof deviation between measured color and target color (block 204). If thecolor is not inside the tolerance band, then an alarm (e.g., a redindicator) is displayed on the console (block 205).

If the color is inside the tolerance band, a determination is made as towhether the color is inside the middle two quartiles of the toleranceband (block 206). If the color is not inside the middle two quartiles ofthe tolerance band, an alarm (e.g., an amber indicator) is displayed(block 207). In the latter regard, it has been found to be convenient touse the red/amber alarm indicator system analogous to the stop/cautionindicators in traffic light systems. If the color is inside the middletwo quartiles of the tolerance band, the target color has been achievedwithin acceptable limits, and the color sensing and control process isterminated (block 210).

Once a red alarm (block 205) or an amber alarm (block 207) is displayed,a further determination is made as to whether a time period of greaterthan the dwell time since the last adjustment in colorant color haspassed. In the latter regard, "dwell time" is defined as the length oftime that it takes for colorants to travel through the extruder. If morethan the dwell time has passed since the last adjustment of coloration,the module 34 instructs the PLC 36 to increase colorant level if coloris too light or to decrease colorant level if the color is too dark(block 209). This process will be described in more detail below withrespect to FIG. 6B. On the other hand, if more than seven minutes hasnot passed since the last adjustment in coloration, no action is taken,and the process merely returns to the color measurement step (block202).

The operations performed by the PLC 36 of FIG. 1 will now be describedwith reference to the flowchart of FIG. 6B. The PLC 36 commencesoperation (block 220), and the operator enters feed settings for thevalves 16 and 18 associated with feeders 12 and 14, respectively, ofFIG. 1 (block 221 of FIG. 6B). The PLC 36 then performs no furtheroperation until it receives input from the module 34 as a result ofcolor measurement performed in accordance with the flowchart of FIG. 6A.If, as a result of the flowchart of FIG. 6A, it is determined that coloradjustment is needed, and if there has been more than seven minutessince the last adjustment in color (see blocks 205, 207 and 208 of FIG.6A), then an increase or decrease in colorant level is indicated, andthe PLC 36 responds to a control input from the module 34 by increasingor decreasing the colorant color according to the color measurement (seeblock 222 of FIG. 6B).

As a next step, the PLC 36 determines whether the feed levels forfeeders 12 and 14 of FIG. 1 are within acceptable limits (block 223). Ifthe feed levels are within acceptable limits, then the PLC 36 awaitsfurther control input from the module 34 and further adjusts colorantcolor based on color evaluation performed by the module 34 (block 222 ofFIG. 6B).

If the feed levels are not within acceptable limits (block 223),original feed settings for the valves 16 and 18 are restored by the PLC36 (block 224 of FIG. 6B), and an alarm is sounded (block 225). Once thealarm is sounded, PLC 36 then awaits further control inputs from theoperator via keyboard 32 or from the module 34 as a result of furthercolor evaluation.

While preferred forms and arrangements have been shown in illustratingthe invention, it is to be understood that various changes andmodifications may be made without departing from the spirit and scope ofthis disclosure.

What is claimed is:
 1. An on-line color monitoring and control system,comprising:feeder means for feeding colorant in a given amount in orderto achieve a desired color of a product; mixer means for mixing saidcolorant in order to obtain said product; light source means forgenerating light and directing said light toward said product so as toproduce reflected light from said product, and producing a referencelight; sensor means responsive to said reflected light and saidreference light for measuring an optical characteristic of said productand providing a color sensor output; and processing means for processingthe color sensor output to generate at least one control signal forprovision to said feeder means, whereby to adjust the given amount ofcolorant fed by said feeder means to said mixer means; wherein saidproduct comprises one of a single moving fiber, a single moving yarn, asingle moving filament of a yarn, and a collection of fibers.
 2. Thesystem of claim 1, further comprising optical switch means disposedbetween said light source means and said sensor means for receiving andswitchably providing said reflected light and said reference light tosaid sensor means.
 3. The system of claim 2, wherein said optical switchmeans comprises:a frame having a recess formed therein, said recesshaving a first portion for receiving an optical fiber element carryingsaid reflected light and a second portion for receiving an optical fiberelement carrying said reference light; a movable member seated withinsaid recess and movable therein, said movable member holding an opticalfiber output element; a motor connected to said movable member formoving said movable member so as to alternately locate said opticalfiber element in said first portion of said recess for contact with saidoptical fiber element carrying said reflected light, and in said secondportion of said recess for contact with said optical fiber elementcarrying said reference light; a shaft connecting said motor to saidmovable member; and an elastic linkage mounted on said shaft andresponsive to movement of said movable member by said motor for creatinga torsional tension firmly pressing said optical fiber element intocontact with said optical fiber elements carrying said reflected lightand said reference light, respectively.
 4. The system of claim 1,wherein said feeder means includes at least one valve responsive to acontrol signal from said processing means for adjusting the given amountof said colorant in order to achieve the desired color of said product.5. The system of claim 1, wherein said mixer means includes an extruderfor performing an extrusion process to obtain said product.
 6. Thesystem of claim 1, further comprising spool means for spooling saidproduct.
 7. The system of claim 6, wherein said sensor means senses thecolor characteristic of said product after spooling.
 8. The system ofclaim 7, wherein said sensor means comprises:a frame; at least oneroller mounted on said frame for contact with said product on said spoolmeans; a first optical fiber for conveying said light directed towardsaid product; and a second optical fiber for conveying said reflectedlight away from said product.
 9. The system of claim 8, wherein saidsensor means further comprises a spring connected to said frame forurging said frame toward said spool means.
 10. The system of claim 6,wherein said sensor means senses said color characteristic of saidproduct prior to spooling.
 11. The system of claim 10, wherein saidsensor means comprises:a guide through which said product passes; afirst optical fiber for carrying said light toward said product as saidproduct passes through said guide; and a second optical fiber forconveying said reflected light away from said product.
 12. The system ofclaim 11, wherein said guide comprises an element having a block mountedon an interior surface of said element, said block having a grooveformed on a surface thereof for conveying said product through saidguide.
 13. The system of claim 1, wherein said sensor means comprises aguide through which said product passes and a detector, and wherein atleast one of said light source means and said detector is disposedinside said guide.
 14. The system of claim 1, wherein said processingmeans comprises:a measurement module for measuring the colorcharacteristic of said product and for comparing the measured colorcharacteristic to a desired color characteristic to obtain an adjustmentoutput; and a controller responsive to said adjustment output forgenerating said at least one control signal for provision to said feedermeans.
 15. The system of claim 14, further comprising operator inputmeans responsive to an operator input for setting said desired colorcharacteristic in said measurement module.
 16. An on-line colormonitoring and control system, comprising:feeder means for feedingcolorant in a given amount in order to achieve a desired color of aproduct; mixer means for mixing said colorant in order to obtain saidproduct; spool means for spooling said product; sensor means for sensinga color characteristic of said product and providing a color sensoroutput; and processing means for processing the color sensor output togenerate at least one control signal for provision to said feeder means,whereby to adjust the given amount of colorant fed by said feeder meansto said mixer means; wherein said sensor means senses said colorcharacteristic of said product after spooling.
 17. The system of claim16, wherein said sensor means comprises:a frame; at least one rollermounted on said frame for contact with said product on said spool means;a first optical fiber for conveying light toward said product; and asecond optical fiber for conveying reflected light away from saidproduct.
 18. The system of claim 17, wherein said sensor means furthercomprises a spring connected to said frame for urging said frame towardsaid spool means.
 19. An on-line color monitoring and control system,comprising:feeder means for feeding colorant in a given amount in orderto achieve a desired color of a product; mixer means for mixing saidcolorant in order to obtain said product; spool means for spooling saidproduct; sensor means for sensing a color characteristic of said productand providing a color sensor output; and processing means for processingthe color sensor output to generate at least one control signal forprovision to said feeder means, whereby to adjust the given amount ofcolorant fed by said feeder means to said mixer means; wherein saidsensor means senses said color characteristic of said product prior tospooling.
 20. The system of claim 19, wherein said sensor meanscomprises:a guide through which said product passes; a first opticalfiber for conveying light toward said product as said product passesthrough said guide; and a second optical fiber for conveying reflectedlight away from said product.
 21. The system of claim 20, wherein saidguide comprises a U-shaped element having a block mounted on an interiorsurface of said U-shaped element, said block having a groove formed on asurface thereof for conveying said product through said guide.
 22. Thesystem of claim 19, wherein said sensor means comprises a guide throughwhich said product passes and a detector disposed inside said guide. 23.A method for monitoring and controlling a color of a product, comprisingthe steps of:(a) feeding colorant in a given amount in order to achievea desired color of said product; (b) mixing said colorant in order toobtain said product; (c) measuring a color characteristic of saidproduct; (d) comparing the measuring color characteristic to the desiredcolor of said product in order to obtain an error; (e) determiningwhether the measured color characteristic falls within a tolerance bandsurrounding the desired color of said product; and (f) adjusting thegiven amount of said colorant fed during step (a) in order to adjust thecolor characteristic of said product; wherein step (e) comprises thesteps of:determining whether the measured color characteristic of saidproduct falls within a first tolerance band surrounding the desiredcolor of said product; displaying a first alarm signal if the measuredcolor characteristic falls outside said first tolerance band;determining whether the measured color characteristic falls within asecond, narrower tolerance band; and displaying a second alarm signal ifsaid measured color characteristic falls outside said second toleranceband.
 24. The method of claim 23, further comprising the steps of:if oneof said first alarm signal and said second alarm signal is displayed,determining whether the amount of colorant has been adjusted within apredetermined amount of time prior to a present time; and wherein step(f) comprises adjusting the amount of said colorant only if the amountof said colorant has not been adjusted within said predetermined periodof time prior to the present time.
 25. The method of claim 23,comprising the step, prior to step (a), of entering feed settings via anoperator input.
 26. A method for monitoring and controlling a color of aproduct, comprising the steps of:(a) feeding colorant in a given amountin order to achieve a desired color of said product; (b) mixing saidcolorant in order to obtain said product; (c) measuring a colorcharacteristic of said product; (d) comparing the measuring colorcharacteristic to the desired color of said product in order to obtainan error; (e) determining whether the measured color characteristicfalls within a tolerance band surrounding the desired color of saidproduct; and (f) adjusting the given amount of said colorant fed duringstep (a) in order to adjust the color characteristic of said product;wherein step (f) comprises the steps of:determining whether the amountof colorant has been adjusted within a predetermined period of timeprior to a present time; and adjusting the amount of colorant only ifthe amount of colorant has not been adjusted within said predeterminedperiod of time prior to the present time.
 27. A method for monitoringand controlling a color of a product, comprising the steps of:(a)feeding colorant in a given amount in order to achieve a desired colorof said product; (b) mixing said colorant in order to obtain saidproduct; (c) measuring a color characteristic of said product; (d)comparing the measuring color characteristic to the desired color ofsaid product in order to obtain an error; (e) determining whether themeasured color characteristic falls within a tolerance band surroundingthe desired color of said product; (f) adjusting the given amount ofsaid colorant fed during step (a) in order to adjust the colorcharacteristic of said product; (g) determining whether the amount ofcolorant fed during step (a) falls within acceptable limits; and (h) ifthe amount of colorant fed during step (a) does not fall withinacceptable limits, restoring original settings of the amount of colorantto be fed.
 28. The method of claim 27, further comprising the step,subsequent to step (h), of displaying an alarm indicating therestoration of original feed settings.